A microfluidic chip that uses a novel technology to identify the presence of circulating proteins in a minuscule blood sample may lead to a new generation of quick and accurate diagnostic tests. The chip’s technology is being developed by Caltech professor of chemistry Dr. James Heath and by Dr. Leroy Hood, the founder of the Institute for Systems Biology, in Seattle.
MIT Technology Review explains:
Heath and Hood’s device, described in this week’s issue of Nature Biotechnology, starts the analysis process with some simple microfluidics. A drop of blood is pulled down a microscale channel by the application of a small external pressure. This first channel branches off into narrower ones, which exclude blood cells and admit the protein-rich blood serum. In typical blood tests, this separation step requires a centrifuge.
The narrower channels are patterned with what Heath calls a protein bar code–lines of DNA bound to antibodies that capture proteins of interest from the serum. After the serum and cells are flushed out, antibodies bound to red fluorescent proteins are flushed in, lighting up captured blood proteins. The protein bar codes can be read under a fluorescent microscope or a gene-chip scanner. The identity of the captured blood proteins can be determined by the location of red lines in the bar code relative to a green fluorescent reference line.
By measuring how much light radiates from a particular protein’s spot in the bar code, Heath and Hood can quantify its concentration in the blood. Heath notes that the chip can measure blood proteins present over a wide concentration range, making it possible to measure not only plentiful blood proteins created by the immune system, but also rarer proteins originating in organs such as the brain. The device is as sensitive as conventional protein tests, and Heath and Hood can measure any proteins they’re interested in by making custom chips with the right antibodies.
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